The Biological Computer Facility of Columbia Universty functions as an interactive system with the Adage display terminal (AGT/50) connected to the IBM 360/91 of the Columbia University Computer Center (CUCC) via the high-speed (10 to the 6th power bits/sec.) link. An investigator can interact with a program running on the Adage computer and through it with a program running on the 360/91. The present system and programs written for it are used for a variety of biological problems. These include: a) molecular model building, energy minimization and fitting of small molecules, proteins, and nucleic acids; b) automatic data collection and analysis of x-ray diffraction film data; c) automatic production of 3-D contour plots, and manipulation and fitting of molecular models into such plots; d) 3-D nerve tracing which can be used along with serial section microscopy to record and analyze spatial relationships between nerve cells and nerve fibers in brains of small animals; e) production of motion pictures which give good 3-D visualization of any object described in the computer. Our present system has one graphics terminal; this restricts the facility to a level of activity much below its potential. We propose to purchase the necessary equipment and develop the software for a small, specialized, message-switching system, so that several display terminals can function simultaneously, with all of them sharing the link to the large 360/91, and the bulk storage devices, plotter/printer, picture scanner, and half-tone picture writer of the Facility. This switching system would also provide two telephone links so that users with their own display terminals could be connected through our system to the same equipment as the local display terminals. There would be a total of three interactive display units by the end of the first year of the grant, and a fourth added the second year. Installation and system programming for this system would be expensive but in the long run efficient, since both the programs and hardware could be made available to additional users at a relatively small incremental cost.